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Data Backup and Recovery
Because data
is the heart of the enterprise, it's crucial for you to
protect it. And to protect your organization's data, you
need to implement a data backup and recovery plan.
Backing
up files can protect against accidental loss of user data,
database corruption, hardware failures, and even natural
disasters. It's your job as an administrator to make sure
that backups are performed and that backup tapes are stored
in a secure location.
Creating a
Backup and Recovery Plan
Data backup
is an insurance plan. Important files are accidentally
deleted all the time. Mission-critical data can become
corrupt. Natural disasters can leave your office in ruin.
With a solid backup and recovery plan, you can recover from
any of these. Without one, you're left with nothing to fall
back on.
Figuring Out a Backup Plan
It takes
time to create and implement a backup and recovery plan.
You'll need to figure out what data needs to be backed up,
how often the data should be backed up, and more. To help
you create a plan, consider the following:
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How
important is the data on your systems? The importance of data can go a long way in helping you determine if
you need to back it up—as well as when and how it should
be backed up. For critical data, such as a database,
you'll want to have redundant backup sets that extend
back for several backup periods. For less important
data, such as daily user files, you won't need such an
elaborate backup plan, but you'll need to back up the
data regularly and ensure that the data can be recovered
easily. |
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What
type of information does the data contain? Data that doesn't seem important to you may be very
important to someone else. Thus, the type of information
the data contains can help you determine if you need to
back up the data—as well as when and how the data should
be backed up. |
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How
often does the data change?
The frequency of change can affect your decision on how
often the data should be backed up. For example, data
that changes daily should be backed up daily. |
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How
quickly do you need to recover the data? Time is an important factor in creating a backup plan. For critical
systems, you may need to get back online swiftly. To do
this, you may need to alter your backup plan. |
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Do you
have the equipment to perform backups? You must have backup hardware to perform backups. To
perform timely backups, you may need several backup
devices and several sets of backup media. Backup
hardware includes tape drives, optical drives, and
removable disk drives. Generally, tape drives are less
expensive but slower than other types of drives. |
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Who will
be responsible for the backup and recovery plan? Ideally, someone should be a primary contact for the
organization's backup and recovery plan. This person may
also be responsible for performing the actual backup and
recovery of data. |
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What is
the best time to schedule backups? Scheduling backups when system use is as low as possible will speed the
backup process. However, you can't always schedule
backups for off-peak hours. So you'll need to carefully
plan when key system data is backed up. |
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Do you
need to store backups off-site?
Storing copies of backup tapes off-site is essential to
recovering your systems in the case of a natural
disaster. In your off-site storage location, you should
also include copies of the software you may need to
install to reestablish operational systems. |
The Basic Types of Backup
There are
many techniques for backing up files. The techniques you use
will depend on the type of data you're backing up, how
convenient you want the recovery process to be, and more.
If you view
the properties of a file or directory in Windows Explorer,
you'll note an attribute called Archive. This attribute
often is used to determine whether a file or directory
should be backed up. If the attribute is on, the file or
directory may need to be backed up. The basic types of
backups you can perform include
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Normal/full backups
All files that have been selected are backed up,
regardless of the setting of the archive attribute. When
a file is backed up, the archive attribute is cleared.
If the file is later modified, this attribute is set,
which indicates that the file needs to be backed up. |
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Copy
backups
All files that have been selected are backed up,
regardless of the setting of the archive attribute.
Unlike a normal backup, the archive attribute on files
isn't modified. This allows you to perform other types
of backups on the files at a later date. |
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Differential backups
Designed to create backup copies of files that have
changed since the last normal backup. The presence of
the archive attribute indicates that the file has been
modified and only files with this attribute are backed
up. However, the archive attribute on files isn't
modified. This allows you to perform other types of
backups on the files at a later date. |
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Incremental backups
Designed to create backups of files that have changed
since the most recent normal or incremental backup. The
presence of the archive attribute indicates that the
file has been modified and only files with this
attribute are backed up. When a file is backed up, the
archive attribute is cleared. If the file is later
modified, this attribute is set, which indicates that
the file needs to be backed up. |
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Daily
backups
Designed to back up files using the modification date on
the file itself. If a file has been modified on the same
day as the backup, the file will be backed up. This
technique doesn't change the archive attributes of
files. |
In your
backup plan you'll probably want to perform full backups on
a weekly basis and supplement this with daily, differential,
or incremental backups. You may also want to create an
extended backup set for monthly and quarterly backups that
includes additional files that aren't being backed up
regularly.
Tip
You'll
often find that weeks or months can go by before anyone
notices that a file or data source is missing. This doesn't
mean the file isn't important. Although some types of data
aren't used often, they're still needed. So don't forget
that you may also want to create extra sets of backups for
monthly or quarterly periods, or both, to ensure that you
can recover historical data over time.
Differential and
Incremental Backups
The
difference between differential and incremental backups is
extremely important. To understand the distinction between
them, examine Table 14-1. As it shows, with differential
backups you back up all the files that have changed since
the last full backup (which means that the size of the
differential backup grows over time). With incremental
backups, you only back up files that have changed since the
most recent full or incremental backup (which means the size
of the incremental backup is usually much smaller than a
full backup).
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